Spontaniety of gas(Nitrogen) adsorption over solid(Zeolite).

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The discussion revolves around the spontaneity of nitrogen adsorption over zeolite, which the user calculated to be non-spontaneous based on the Gibbs free energy equation. They used the heat of vaporization and entropy values for nitrogen in gas and liquid states to arrive at a positive dG value, indicating non-spontaneity. The user speculates that external factors, such as pressure, might influence the adsorption process, potentially leading to a negative dG in practical scenarios. They express confusion over the discrepancy between their calculations and observed adsorption behavior at 300K. Clarification on the role of pressure and other conditions in adsorption spontaneity is sought.
AbhiNature
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Hello!

The other day I was reading about adsorption(gas over solid), and there it stated that it is a spontaneous process. I wanted to know how spontaneous the process is. I therefore took nitrogen adsorption over zeolite as a candidate to find its spontaneity, and to my surprise, my calculations showed it to be a non-spontaneous process. I guess I am wrong somewhere, but I just cannot find where.

Following are the calculations that I did;
dG = dH - T*dS
Assuming adsorption to be equivalent to converting gas to liquid.
Therefore,
dH = Heat of vaporization of Nitrogen = -5560J/mole
T = 300K (Adsorption at 300K).
S1 = Entropy of Nitrogen at 300K = 192J/moleK.
S2 = Entropy of Nitrogen in liquid form (I did not find entropy data of liquid Nitrogen, but I did find data at 100K) = 160J/moleK.

Which gives,
dG = 4040J/mole - non-spontaneous.

I saw a graph which showed quite a lot of adsorption at 300K.

I speculate that, adsorption needs pressure and the source of this pressure has more than enough negative dG?

Could you please help me understand this?

Thanks!
 
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